Three major areas of theoretical population genetics are to be studied. Our work on linkage and selection will take three new directions. The first is the study of models of fertility selection at two loci under random mating. The second is the study of viability selection at linked loci in which the mating system includes mixtures of regular inbreeding and outcrossing. The third is the evolutionary theory of genetic modifiers introduced at mutation-selection balance of the major loci. The second major area is the quantitative theory of evolution under more general modes of transmission than Mendelian genetics. This includes the dynamics and statistics of intra- and extrafamilial transmission of traits whose rates of contact and fitness are genotype dependent. The third major area includes population genetic modelling of individually disadvantageous traits. The main questions here include the extent to which commonly accepted theory depends on the assumption of complete altruism in at least one genotype and what modifications are required if the model "altruism" includes two loci. The theory will be developed analytically and where ever necessary with the aid of numerical computation.